1. Field of Invention
The invention relates to a light starter and, in particular, to a light starter using piezoelectric ceramics as its transformer to drive a cold cathode fluorescent light (CCFL).
2. Related Art
The CCFL has wide applications, such as backlit sources of liquid crystal displays, scanners, multiple function peripherals (MFP's), etc. Other devices such as transparent media adaptors (TMA's), scanning of negative films or XPA's also use the CCFL as their light sources.
Since the CCFL requires an extremely high voltage (hundreds of volts) during initialization and work, its driver or light starter has to be able to provide such high-voltage power output. The output power quality of the driver determines the brightness and stability of the CCFL.
Normally, the CCFL is driven by a transformer. The transformer is an electronic oscillatory circuit with two or more sets of coils. Inductance happens via air or iron cores between the coils to produce coupled signals. According to the electromagnetic inductance rule, the electric voltage is raised or lowered to drive the CCFL. The electronic oscillatory circuit is limited by the physical material properties of the coiled transformer so that the voltage conversion efficiency is worse. The voltage conversion loss is thus higher.
Although the traditional copper-wire-iron-core transformers are very popular and there exists a more mature technology, there are still some drawbacks in practical uses. For example, it is possible for them to be on fire and smoky when the temperature is high or the power supply is not stable. On the other hand, using electromagnetic coils is likely to produce electromagnetic interference (EMI). Moreover, the volume of the traditional transformers tends to be larger.
In summary, the coiled transformer and the PWM circuit determines the light output conversion efficiency and whether the driver circuit is stable. If the CCFL initialization time can be greatly reduced and the conversion efficiency of the coiled transformer can be increased, the brightness of the CCFL can be more stable while its lifetime is longer.